OTTAWA - Employees doing personal business on a company computer should have a reasonable expectation that their business is private, the Supreme Court of Canada said Friday.

And while that expectation is a limited one, it does extend to employers being unable to simply turn illegal material over to police, the top court said.

It ordered a new trial for teacher Richard Cole, who had argued his charter right to freedom from unreasonable search was violated when his school principal turned over his hard drive to police.

On the computer were pictures of a nude student that Cole had taken off another student's computer, which he had access to as part of his job.

They were discovered by a technician and the entire laptop was turned over to police, who never obtained a warrant for the material believing the school had the authority to turn it over.

"Computers that are reasonably used for personal purposes — whether found in the workplace or the home — contain information that is meaningful, intimate, and touching on the user’s biographical core," Justice Morris Fish wrote in the 6-1 decision.

"Vis-a-vis the state, everyone in Canada is constitutionally entitled to expect privacy in personal information of this kind."

But because Cole's school had policies on the personal use of computers that expressly stated his supervisors would have access, his expectation of privacy should have been limited, the court found.

Cole's case was thrown out by lower courts because police didn't get a warrant to obtain the material, and instead just took it from the school board after it was discovered.

A Court of Appeal overturned that decision and ordered a new trial but didn't allow much of the evidence, except a copy of the photographs made by the technician.

The Supreme Court ruled that the warrantless search was not an egregious breach of charter rights and that admitting all the evidence from the computer at trial would not bring the administration of justice into disrepute.

"The exclusion of the material would have a marked negative impact on the truth-seeking function of the criminal trial process."

The court said Cole did have a reasonable expectation of privacy with the computer, but if police had asked for a warrant, they would have received one and found the evidence.

"The school board was legally entitled to inform the police of its discovery of contraband on the laptop," Fish wrote. "This would doubtless have permitted the police to obtain a warrant to search the computer for the contraband.

"But receipt of the computer from the school board did not afford the police warrantless access to the personal information contained within it."

At the same time, the school board didn't have the right to violate Cole's privacy, Fish argued.

Justice Rosalie Abella dissented, saying the police search without a warrant was a serious breach of charter rights.

"The impact of the breach on the accused’s charter-protected interests, even assuming that his reasonable expectation of privacy was reduced because it was a workplace computer, was significant given the extent of the intrusion into his privacy," Abella wrote.

"The warrantless search and seizure in this case included the entire contents of the accused’s computer. It had no restrictions as to scope."

Cole had been charged with possession of child pornography and unauthorized use of a computer.

The case is unique in that he had access to a Charter argument because school boards are covered by that constitutional document, while employees in private companies don't necessarily have the same legal remedies.

But privacy experts have noted there is a message to private sector employers about the need for clear policies on personal use of workplace machines.